Basic Research Needs for Geosciences - Energetics Meetings and ...

PRIORITY RESEARCH DIRECTION: TRANSPORT PROPERTIES AND IN SITU CHARACTERIZATIONOF FLUID TRAPPING, ISOLATION, AND IMMOBILIZATIONto our ability to successfully engineer a manmade repository for energy waste. We currently havelimited understanding of how trapping mechanisms operate under in situ conditions. Our abilityto detect and characterize the dominant mechanisms within a given reservoir at depth is similarlylimited.Interfacial and surface properties of fluids in fine-grained and fractured mediaInterfacial tension between fluid phases and surface tension between fluid and solid are thefundamental forces that control the flow of multiphase fluids through porous media. As pore sizedecreases, the radius of curvature of fluid interfaces decreases, causing interfacial forces to riseto levels that are a significant fraction (ranging from > 10% to several times) of the gravitationalforces that drive fluid flow. When the surface forces are greater than the gravitational forces,fluids can be trapped in porous media.Interfacial and surface tension of multicomponent fluids is rarely measured, and is one of thepoorly predicted physical parameters in currently available simulators of thermochemical andphysical properties of fluid mixtures and fluid-rock properties. In addition, interfacial processesare dramatically impacted by abiotic and biologically mediated chemical reactions. Also, thekinetics of many mineral-fluid and fluid-fluid reactions are slow, making examination of theirimpacts on interfacial properties exceedingly difficult.Conductivity of faults and fracturesIt is critically important to be able to predict whether faults or other local crosscuttingheterogeneities (e.g., clastic dikes, etc.) conduct or retain fluids as a function of fluid pressure,phase state, and chemical composition. Furthermore we need to be able to predict the impacts ofanthropogenic perturbations on the conductivity of these structures to buoyant fluids (see Figure43). Presently available wellbore-based characterization tools are either poorly suited orcompletely inadequate for characterizing these effects. Fault gouge properties and complex 3Dfracture networks in natural systems are very difficult, or even impossible, to reproduce in alaboratory setting, making field measurements a critical but expensive and time-consumingaspect of this research. Finally, the typically slow rate of fluid migration in these structuresmakes conducting measurements in a timely manner challenging, even under favorableconditions.In situ measurement of fluid-rock interactions in fine-grained mediaLow-permeability media (barriers to flow) are elements that define the pathways of fluidmigration at the basin scale in many subsurface settings. Fine-grained rocks, low permeabilitysalt or anhydrite, and faults with gouge are examples of barriers. These featurescompartmentalize pressure, trap buoyant fluids, and isolate compositionally different fluids. Theperformance of these barriers in the presence of multicomponent fluids is complex, because theactive sealing mechanism varies with fluid composition and pressure, and geochemical and stresschanges can alter the properties of the seal.Basic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems 133